Are Bifidobacterium Species Key Players in the Progression of Type 1 Diabetes? A Systematic Review.

BACKGROUND: Type 1 diabetes (T1D) frequently develops in childhood and is preceded by a non-symptomatic period of autoimmunity. Alterations in the gut microbiome are implicated in T1D pathogenesis. Bifidobacterium is a significant focus due to its positive health impacts, association with breastfeeding and presence in probiotics and infant milk-formulas. This systematic review aims to investigate Bifidobacterium's association with T1D across disease stages. METHODS: A comprehensive electronic search was conducted in MEDLINE, EMBASE and Web of Science, from 2011 to 2024. The search used a combination of medical subject headings and keywords related to Bifidobacterium. Studies included individuals at risk of T1D (pre-stage, stage 1 or 2 asymptomatic T1D) and with stage 3 symptomatic T1D while excluding T2D, clinical trials and animal studies. RESULTS: The search initially retrieved 1120 articles. Of these, 25 papers met the inclusion criteria, covering 4533 individuals (842 cases with or at-risk of T1D and 3691 healthy controls). The studies highlighted variability in Bifidobacterium abundance in T1D, with higher abundance found more often in at-risk asymptomatic individuals and lower abundance frequently found in those with established T1D. CONCLUSION: These findings do not support loss of Bifidobacterium as a key factor in the early development of T1D. Further studies are needed to explore Bifidobacterium's role in T1D progression and management.